Willam Shewhart
Willam Shewhart

Walter Shewhart is often referred to as the “Father of Quality Control” – he worked as a process engineer for Western Electric and then at Bell Labs.  He retired in the mid 50’s.  Juran actually worked under Shewhart

Six Sigma as a measurement standard in product variation can be traced back to the 1920’s when Walter Shewhart showed that three sigma from the mean is the point where a process requires correction.

Walter Andrew Shewhart was an American Physicist and statistician, he is referred as the ‘Father of Statistical Quality Control’. Walter Andrew Shewhart was born to Anton and Esta Barney Shewhart in New Canton, Illinois in the year 1891. He did his Master’s in the University of Illinois. Later, he attended the University of California at Berkeley to pursue Ph.D. degree where he received a Doctorate in physics in 1917. He worked as a professor in both the universities then he worked as head the department of physics at Wisconsin Normal School, Lacrosse.

In 1918, Walter Shewhart worked at the Western Electric Company, one of the largest hardware manufacturers during that time. He assisted engineers in the manufacturing plant in refining the quality of telephone hardware. Later Shewart went to work at Hawthorne until 1925, then he worked at the Bell Telephone Research Labs and worked there until his retirement.

Walter Shewhart developed modern statistical concepts and scientific methods to minimize the human efforts. Shewhart’s methods influenced other statisticians like W Edwards Deming and Joseph Juran. These three people Shewhart, Deming, and Juran are referred as the three authors of the quality upgrading movements. Shewhart’s work specifically, control charts and the PDSA cycle influenced the daily work of quality extensively.

Reducing Variation – To Improve Quality

The emphasis on reducing variation to enhance quality is a great contribution to quality management. Reducing variation to improve quality resulted in manufacture of precise things. The concept was applicable in different fields like automobiles, electronics and constructions etc.

Shewhart acknowledged two classes of variation namely ‘special‐cause’ and ‘common‐cause variation. These two categories can also be termed as ‘assignable‐cause’ and ‘chance‐cause’’ variation respectively. A control chart was designed by him to explain these two categories of variations. Shewhart proposed new attributes and variables in his control charts. Shewhart proposed that to improve quality and reduce scrap, common-cause variation should be controlled. In this way, any process can be brought under statistical control. In order to distinguish between special cause and common cause variations, first the process should be brought to a state of statistical control. After bringing a process to this state, it would be likely easy to forecast future outputs and also to manage processes in economical ways. Shewhart’s principle paved way for modern scientific analysis of process control.

The objective of any industry is to develop economic methods to satisfy the human needs. This should be done by reducing the things to routines necessitating very little human effort. By making use of scientific techniques and modern statistical theories, it was possible to set up limits for the results of routine efforts economically. If the results of any routine process deviate away from the limits, it is said that the routine has broken down and will no longer be economical. The cause of trouble must be identified and eliminated in order to make the process economical.

Six Sigma Concept

‘Sigma’ is a Greek letter, it is a mathematical term which is used to denote standard deviation. It is a standard statistical unit used to measure and describe the distribution of any process about its mean.

Shewhart’s ideas and statistical concepts were embraced in clinical laboratories for several years. Clinical laboratories used these concepts in proficiency testing and quality control operations. Many industries have re-discovered Shewhart’s methods and tools of statistical process control which is named as ‘Six Sigma’. Recently Motorola Company has also made use of Six Sigma methods for improving product quality. Motorola Inc. was awarded Malcolm Baldrige National quality award in the manufacturing category for using Six Sigma concepts for quality improvement. In recent times, Six Sigma concept has acquired public attention extensively. Many other organizations also started using Six Sigma concept popularizing it.

ASQ – American Society for Quality

ASQ of individuals who are passionate about methods of quality control. Members of ASQ contribute to industry with their ideas of quality control and experience. Shewhart was ASQ’s first honorary associate, he efficaciously brought together the principles of statistics, economics and engineering. Shewhart developed highly effective tools specifically control charts, his contributions were widely recognized.

Shewhart acquired appreciation in the statistical community for writing Statistical Method from the Viewpoint of Quality Control. There is a number of articles and journals written by him were initially held within Bell Laboratories which were later published.

Another important element in Shewhart’s achievements was his quality of bringing out ideas and knowledge of other individuals.

Shewhart always believed that statistical theory would serve the needs of industry. He was a man of science who worked patiently to develop ideas which made the world better. ASQ is influenced intensely by Shewhart’s contributions and ideas. Before his death, Shewhart mentioned to other members of ASQ that he was pleased by their contributions which led to extensive growth in the field of quality control. He also stated that the he was astonished by looking at the development which was beyond his expectations.


Comments (6)

There are a lot of misleading articles about the origin of the TQM concepts. You’ve demystified some of my doubts. Thank you!

Should this statement, “Shewhart proposed that to improve quality and reduce scrap, common-cause variation should be controlled,” not be “Shewhart proposed that to improve quality and reduce scrap, special-cause variation should be controlled”?

Hi Matt,

I think your question is really about the difference between common cause variation and special cause variation.

As you standardize a process you’ll have common cause variations. You can then improve those common cause variations.

Special cause variation are those truly unique situations that are by definition difficult to control. You can try to avoid them (eg with checksheets) or mitigate them (eg with a FMEA) – but it’s hard to even tell if your process even has experienced a special cause variation until you’ve standardized the process and brought common cause variation under some kind of control.

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